Point-of-care (POC) testing refers to performing medical diagnostic tests at the time and place (“point of care”) that the patient is being treated. Point-of-care testing is advantageous over traditional diagnostic testing where patient samples are sent out to a laboratory for further analysis, because the results of traditional diagnostic tests may not be available for hours, if not days or weeks, making it difficult for a caregiver to assess the proper course of treatment in the interim.
Although some POC testing devices are available, they typically suffer from one or more serious drawbacks. For example, many POC testing devices can analyze only one target analyte at a time. And while some POC testing devices can perform multiplexed analysis, e.g., by testing multiple analyte targets in one test cartridge, such POC devices typically suffer from serious drawbacks, such as the inability to precisely control the volume of blood sample dispensed for each analysis, which adversely affects the accuracy of the POC testing.
Designing POC testing devices for in-home is particularly challenging, because such devices are often operated by people with limited training or no training at all. Current systems can often require the user to follow multiple steps of operations of multiple separated parts (pipettes, test strips, etc.). User-introduced errors can easily cause inaccurate or failed assays. To avoid user-introduced errors, current POC devices separate sample collection, sample preparation, and the assay to avoid common problems such as timing inconsistencies, inaccurate sample volume, air bubble formation, and other issues. However, this approach presents other challenges. For example, sample collection is often done using plastic pipettes or glass capillaries that need to be filled up to a given mark. Accuracy of an assay depends on the accuracy of a sample volume, which in turn relies on relies on a user's ability to consistently and accurately fill a capillary or pipette to collect the appropriate sample volume. One of the biggest problems relating to accurate sample collection is the creation of undesirable air bubbles during the collection process. It can be difficult to fill the capillary in a single motion, and thus users often use several stop-and-fill motions, which may temporarily leave the tip of the capillary exposed to air rather than the desired fluid analyte (e.g., blood). When this happens, air bubbles can then get into the capillary or pipette and prevent the collection of the appropriate volume of fluid analyte, thereby introducing errors in the sample volume.
In addition to problems associated with inaccurate sample volume collection, additional problems may arise when conducting the assay or assays associated with a conventional POC testing system. For example, after a sample is collected, POC systems can require the user to manually dispense the blood sample from the pipet or capillary to the cartridge that can perform the assay. In this step, additional user-introduced error such as mis-aiming, touching the assay pad, or incomplete or prolonged dispensing can further adversely affect the accuracy assay results. For instance, in most point-of-care (POC) testing systems for blood samples, certain sample preparation steps need to be performed prior to a final chemical reaction that provides the test result. These sample preparation steps may include complex preparation steps such as plasma separation, cell lysis, or others, depending on the assay. The time required to complete such complex preparation steps may be comparable to the time required for blood to undergo undesirable clotting, which further introduces error into the assay results. Thus, it would be desirable to have a POC system that precisely controls the amount of analyte that is collected, minimizes the analyte collection time to avoid undesirable side reactions (e.g., blood clotting); and controls the dispensing time during which the target analyte undergoes chemical reactions with the assay chemicals to provide an assay result.